This invention relates generally to roll-over valves. More particularly, it relates to a roll-over valve which is adapted for mounting on an automotive vehicle fuel tank.
In order to comply with evaporative emission requirements, automotive vehicles are today typically equipped with a vapor control system, commonly referred to as an evaporative emission control system. The usual evaporative emission control system comprises a cannister which is connected to the headspace of the fuel tank by a conduit and which contains a medium capable of adsorbing fuel vapors. When temperature and pressure conditions are such that the fuel vapor pressure in the tank headspace increases beyond a certain threshold, vapors are allowed to pass through the conduit to the cannister where they are collected. In this way, the uncontrolled escape of vapor to atmosphere is avoided. Because the capacity of the medium in the cannister is limited, purging of the cannister takes place at certain times, and there are various known techniques for accomplishing cannister purging, including a return venting of the cannister back to the tank through the conduit under certain conditions conducive to return venting.
A further requirement which has been imposed on automotive vehicles relates to leakage of liquid fuel in the event of vehicle roll-over. In order to comply with this requirement, a roll-over valve is typically placed in the conduit from the fuel tank to the vapor control system cannister. A roll-over valve is an attitude-responsive device which remains open so long as the vehicle is operating in the usual manner over relatively flat terrain or up and down hills. If however the vehicle should roll over, the roll-over valve operates to close the conduit between the fuel tank and the cannister so that fuel does not leak out through the conduit and cannister.
The amount of attitude change which is required to operate a roll-over valve from open to closed position depends to a certain extent on the design of the valve itself. Some designs require 90.degree. or more change, whereas others require a lesser amount of change to close the valve.
For example U.S. Pat. No. 4,095,609 illustrates a roll-over valve which utilizes a caged sphere disposed on a conically tapered seat. When the valve is upright, the sphere seats at the center of the conically tapered seat and causes the cage to assume a full down position so that the valve is open. A change in attitude of the valve in any direction will cause the sphere to roll off the center of the conical seat. The interaction of the rolling sphere with the cage causes the cage to be displaced away from the conical seat and operate the valve toward the closed position. At a predetermined amount of tipping or attitude change, the sphere will have rolled sufficiently from the center of the conical seat to cause the valve to close. Other types of attitude-responsive valves are illustrated in U.S. Pat. Nos. 2,396,233; 1,683,338; 1,942,630; 4,325,398; and 4,487,215.
Various types of valve mechanisms can also associate with the fuel tank closure cap for the purpose of relieving or venting the tank. Generally these valve mechanisms are intended to open under extreme vapor conditions which cannot be relieved by the cannister control system. In other words, they are really in the nature of a safety which vents the tank directly to atmosphere under extreme pressure conditions. Other patents relating to fuel tank venting and/or roll-over are: U.S. Pat. Nos. 3,938,692; 3,996,951; 3,568,695; 4,162,021; 4,000,828; 3,757,987; 4,033,475; 4,285,440; 1,893,942; 4,023,583; 3,985,260; and 4,457,325.
The present invention is directed to a new and improved roll-over valve which offers important advantages and benefits over prior valves.
One important advantage of the present invention is that the roll-over valve is well-suited for mounting directly on the fuel tank with a portion of the valve body being actually disposed in the headspace of the tank so that the main valve member and main orifice are exposed directly to the headspace. With the valve so disposed, even though at virtually the highest point of the tank, the valve is still subject to the liquid fuel swashing about in the tank, and intrusion of liquid fuel into the vapor control system is undesirable. One of the features of the present invention is a unique configuration which serves to shed the liquid fuel away from the main valve member and main orifice so that intrusion of liquid fuel through the main orifice and into the vapor control system is minimized or even eliminated.
Another important feature of the invention relates to an associated valving mechanism which provides pressure relief and return vent functions in association with the vapor control system. The valve of the present invention comprises a relief valve member which has a cooperative association with the main orifice so that above a predetermined pressure in the tank, the tank's headspace is relieved to the vapor control system. A return vent valve is carried by the relief valve member to allow return vent flow from the vapor control system back to the tank when conditions in the vapor control system relative to those in the headspace of the tank are conducive to such return venting. This is useful for cannister purging.
The vent valve member comprises a disc which is captured within a depression in the relief valve member by a retainer member. The disc has the ability to float radially with a pocket of the retainer member such that for any radial position within the pocket, proper operation is assured.
The preferred embodiment has a construction which is especially advantageous in its organization and arrangement. It has a number of parts which fit together without the need for extra attaching parts. It is also compact and has only a small number of individual component parts. It is efficient in its use of materials and is especially cost effective for the functions which it performs.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.